Dell SmartFabric OS10 User Guide Release 10.5.3

Another way to organize routers within an AS and reduce the mesh for IBGP peers is to configure BGP confederations. As with route reflectors, Dell Technologies recommends BGP confederations only for IBGP peering involving many IBGP peering sessions per router.

When you configure BGP confederations, you break the AS into smaller sub-ASs. To devices outside your network, the confederations appear as one AS. Within the confederation sub-AS, the IBGP neighbors are fully meshed and the MED, NEXT_HOP, and LOCAL_PREF attributes maintain between confederations.

1. Enter the confederation ID AS number in ROUTER-BGP mode (1 to 65535 for 2–byte, 1 to 4294967295 for 4–byte).

   confederation identifier as-number

2. Enter which confederation sub-AS are peers in ROUTER-BGP mode, from 1 to 65535 for 2–byte, 1 to 4294967295 for 4–byte. All Confederation routers must be either 4 bytes or 2 bytes. You cannot have a mix of router ASN support.

   confederation peers as-number [... as-number]

Configure BGP confederations

OS10(config)# router bgp 65501
OS10(conf-router-bgp-65501)# confederation identifier 100
OS10(conf-router-bgp-65501)# confederation peers 65502 65503 65504
OS10(conf-router-bgp-65501)# neighbor 1.1.1.2
OS10(conf-router-neighbor)# remote-as 65502
OS10(conf-router-neighbor)# no shutdown
OS10(conf-router-neighbor)# exit
OS10(conf-router-bgp-65501)# neighbor 2.1.1.2
OS10(conf-router-neighbor)# remote-as 65503
OS10(conf-router-neighbor)# no shutdown
OS10(conf-router-neighbor)# exit
OS10(conf-router-bgp-65501)# neighbor 3.1.1.2
OS10(conf-router-neighbor)# remote-as 65504
OS10(conf-router-neighbor)# no shutdown
OS10(conf-router-neighbor)# exit
OS10(conf-router-bgp-65501)# end
OS10# show running-configuration bgp
!
router bgp 65501
 confederation identifier 100
 confederation peers 65502 65503 65504
 !
 neighbor 1.1.1.2
  remote-as 65502
  no shutdown
 !
 neighbor 2.1.1.2
  remote-as 65503
  no shutdown
 !
 neighbor 3.1.1.2
  remote-as 65504
  no shutdown